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meta (version 4.6-0)

metagen: Generic inverse variance meta-analysis

Description

Fixed and random effects meta-analysis based on estimates (e.g. log hazard ratios) and their standard errors; inverse variance weighting is used for pooling.

Usage

metagen(TE, seTE, studlab, data=NULL, subset=NULL, sm="", level=.settings$level, level.comb=.settings$level.comb, comb.fixed=.settings$comb.fixed, comb.random=.settings$comb.random, hakn=.settings$hakn, method.tau=.settings$method.tau, tau.preset=NULL, TE.tau=NULL, tau.common=.settings$tau.common, prediction=.settings$prediction, level.predict=.settings$level.predict, method.bias=.settings$method.bias, n.e=NULL, n.c=NULL, backtransf=.settings$backtransf, pscale=1, irscale = 1, irunit = "person-years", title=.settings$title, complab=.settings$complab, outclab="", label.e=.settings$label.e, label.c=.settings$label.c, label.left=.settings$label.left, label.right=.settings$label.right, byvar, bylab, print.byvar=.settings$print.byvar, byseparator = .settings$byseparator, keepdata=.settings$keepdata, warn=.settings$warn)

Arguments

TE
Estimate of treatment effect.
seTE
Standard error of treatment estimate.
studlab
An optional vector with study labels.
data
An optional data frame containing the study information.
subset
An optional vector specifying a subset of studies to be used.
sm
A character string indicating underlying summary measure, e.g., "RD", "RR", "OR", "ASD", "HR", "MD", "SMD", or "ROM".
level
The level used to calculate confidence intervals for individual studies.
level.comb
The level used to calculate confidence intervals for pooled estimates.
comb.fixed
A logical indicating whether a fixed effect meta-analysis should be conducted.
comb.random
A logical indicating whether a random effects meta-analysis should be conducted.
prediction
A logical indicating whether a prediction interval should be printed.
level.predict
The level used to calculate prediction interval for a new study.
n.e
Number of observations in experimental group.
n.c
Number of observations in control group.
hakn
A logical indicating whether method by Hartung and Knapp should be used to adjust test statistics and confidence intervals.
method.tau
A character string indicating which method is used to estimate the between-study variance $\tau^2$. Either "DL", "PM", "REML", "ML", "HS", "SJ", "HE", or "EB", can be abbreviated.
tau.preset
Prespecified value for the square-root of the between-study variance $\tau^2$.
TE.tau
Overall treatment effect used to estimate the between-study variance tau-squared.
tau.common
A logical indicating whether tau-squared should be the same across subgroups.
method.bias
A character string indicating which test is to be used. Either "rank", "linreg", or "mm", can be abbreviated. See function metabias
backtransf
A logical indicating whether results should be back transformed in printouts and plots. If backtransf=TRUE (default), results for sm="OR" are printed as odds ratios rather than log odds ratios and results for sm="ZCOR" are printed as correlations rather than Fisher's z transformed correlations, for example.
pscale
A numeric defining a scaling factor for printing of single event probabilities, i.e. if argument sm is equal to "PLOGIT", "PLN", "PRAW", "PAS", or "PFT". See also metaprop
irscale
A numeric defining a scaling factor for printing of rates, i.e. if argument sm is equal to "IR", "IRLN", "IRS", or "IRFT".
irunit
A character specifying the time unit used to calculate rates, e.g. person-years.
title
Title of meta-analysis / systematic review.
complab
Comparison label.
outclab
Outcome label.
label.e
Label for experimental group.
label.c
Label for control group.
label.left
Graph label on left side of forest plot.
label.right
Graph label on right side of forest plot.
byvar
An optional vector containing grouping information (must be of same length as TE).
bylab
A character string with a label for the grouping variable.
print.byvar
A logical indicating whether the name of the grouping variable should be printed in front of the group labels.
byseparator
A character string defining the separator between label and levels of grouping variable.
keepdata
A logical indicating whether original data (set) should be kept in meta object.
warn
A logical indicating whether warnings should be printed (e.g., if studies are excluded from meta-analysis due to zero standard errors).

Value

An object of class c("metagen", "meta") with corresponding print, summary, plot function. The object is a list containing the following components:

Details

Generic method for meta-analysis, only treatment estimates and their standard error are needed. The method is useful, e.g., for pooling of survival data (using log hazard ratio and standard errors as input). The inverse variance method is used for pooling.

For several arguments defaults settings are utilised (assignments with .settings$). These defaults can be changed using the settings.meta function.

Internally, both fixed effect and random effects models are calculated regardless of values choosen for arguments comb.fixed and comb.random. Accordingly, the estimate for the random effects model can be extracted from component TE.random of an object of class "meta" even if argument comb.random=FALSE. However, all functions in R package meta will adequately consider the values for comb.fixed and comb.random. E.g. function print.meta will not print results for the random effects model if comb.random=FALSE.

A prediction interval for treatment effect of a new study is calculated (Higgins et al., 2009) if arguments prediction and comb.random are TRUE.

R function update.meta can be used to redo the meta-analysis of an existing metagen object by only specifying arguments which should be changed.

For the random effects, the method by Hartung and Knapp (2003) is used to adjust test statistics and confidence intervals if argument hakn=TRUE. The DerSimonian-Laird estimate (1986) is used in the random effects model if method.tau="DL". The iterative Paule-Mandel method (1982) to estimate the between-study variance is used if argument method.tau="PM". Internally, R function paulemandel is called which is based on R function mpaule.default from R package metRology from S.L.R. Ellison . If R package metafor (Viechtbauer 2010) is installed, the following methods to estimate the between-study variance $\tau^2$ (argument method.tau) are also available:

  • Restricted maximum-likelihood estimator (method.tau="REML")
  • Maximum-likelihood estimator (method.tau="ML")
  • Hunter-Schmidt estimator (method.tau="HS")
  • Sidik-Jonkman estimator (method.tau="SJ")
  • Hedges estimator (method.tau="HE")
  • Empirical Bayes estimator (method.tau="EB").

For these methods the R function rma.uni of R package metafor is called internally. See help page of R function rma.uni for more details on these methods to estimate between-study variance. Argument pscale can be used to rescale proportions, e.g. pscale=1000 means that proportions are expressed as events per 1000 observations. This is useful in situations with (very) low event probabilities.

Argument irscale can be used to rescale rates, e.g. irscale=1000 means that rates are expressed as events per 1000 time units, e.g. person-years. This is useful in situations with (very) low rates. Argument irunit can be used to specify the time unit used in individual studies (default: "person-years"). This information is printed in summaries and forest plots if argument irscale is not equal to 1.

References

Cooper H & Hedges LV (1994), The Handbook of Research Synthesis. Newbury Park, CA: Russell Sage Foundation.

DerSimonian R & Laird N (1986), Meta-analysis in clinical trials. Controlled Clinical Trials, 7, 177--188.

Higgins JPT, Thompson SG, Spiegelhalter DJ (2009), A re-evaluation of random-effects meta-analysis. Journal of the Royal Statistical Society: Series A, 172, 137--159.

Knapp G & Hartung J (2003), Improved Tests for a Random Effects Meta-regression with a Single Covariate. Statistics in Medicine, 22, 2693--2710, doi: 10.1002/sim.1482 .

Paule RC & Mandel J (1982), Consensus values and weighting factors. Journal of Research of the National Bureau of Standards, 87, 377--385.

Viechtbauer W (2010), Conducting Meta-Analyses in R with the Metafor Package. Journal of Statistical Software, 36, 1--48.

See Also

update.meta, metabin, metacont, print.meta

Examples

Run this code
data(Fleiss93)
meta1 <- metabin(event.e, n.e, event.c, n.c, data=Fleiss93, sm="RR", method="I")
meta1

#
# Identical results by using the following commands:
#
meta1
metagen(meta1$TE, meta1$seTE, sm="RR")

forest(metagen(meta1$TE, meta1$seTE, sm="RR"))


#
# Meta-analysis with prespecified between-study variance
#
summary(metagen(meta1$TE, meta1$seTE, sm="RR", tau.preset=sqrt(0.1)))


#
# Meta-analysis of survival data:
#
logHR <- log(c(0.95, 1.5))
selogHR <- c(0.25, 0.35)

metagen(logHR, selogHR, sm="HR")


#
# Paule-Mandel method to estimate between-study variance
# Data from Paule & Mandel (1982)
#
average <- c(27.044, 26.022, 26.340, 26.787, 26.796)
variance <- c(0.003, 0.076, 0.464, 0.003, 0.014)
#
summary(metagen(average, sqrt(variance), sm="MD", method.tau="PM"))

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